The present invention relates to wireless communication systems.
Generally, wireless communication systems include multiple base stations in different geographic areas. Each base station provides services for remote units within the base station's geographic area.
Base stations and remote units are distinguishable. Generally, remote units include termination devices in a wireless communication system. In contrast, a base station is not a termination device. Rather, a base station usually relays traffic between or among termination devices. Another distinguishing feature between a base station and a remote unit is that a base station can simultaneously communicate with multiple remote units while a remote unit usually communicates with only one base station (except in certain situations such as handover).
Remote units include cellular phones. Although cellular telephones were initially limited to bulky systems installed in automobiles, they have developed into more compact, portable, and multi-functional voice and data-capable communication devices. Remote units also include other types of stationary and mobile wireless communication devices, any of which may provide wireless communication and processing of any combination of voice and data signals using any combination of analog and digital techniques. Such devices include, but are not limited to, cellular-type voice and data handsets, wireless modems (e.g., PCMCIA) for portable or fixed computing systems, wireless personal digital assistants, wireless two-way pagers, and wireless Web pads.
Remote units are operable in various types of wireless communication system architectures and protocols, including but not limited to cellular systems (e.g., AMPS, CDMA, GSM, and PHS), wireless local area network (“WLAN”), microwave point-to-multipoint systems, and so forth. Remote units typically provide various types of voice and/or data communication functionalities (also referred to as requested services) that may be enabled by hardware, software, or any combination thereof.
To facilitate processing and communication of voice and data signals, remote units may include a display, a numeric or alphanumeric keypad, pointing device, speaker and/or microphone, digital video/photo camera, data storage, Web browsing capability, instant/text messaging capability, and a graphical user interface.
Some remote units, such as cellular phones, are mobile. Usually, mobile remote units are designed to be relatively small in size in order to facilitate portability. Such remote units typically have a relatively small antenna and power source, such as a small rechargeable battery having a limited power capacity. As a result, remote units may be more susceptible to interference and other types of transmission (Tx) and/or reception (Rx) performance degradation and may suffer from limited power resources. Generally, the performance level of a remote unit indicates how well the remote unit is communicating with other devices. In most wireless communication systems, performance is measured by some probability of error, Pe, in signal processing. Examples of a probability of error include bit error rate (“BER”) and frame error rate (“FER”). Other indicia of performance include metrics of signal quality, such as a signal to noise ratio (“SNR”) or a signal to interference and noise ratio (“SINR”), and receive signal strength indication (“RSSI”).